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Message-ID: <CALPaoCjN7-1fBF+6x1X4SfhRyx6L8aWaOfqOLQzKMRp=zHiyFg@mail.gmail.com>
Date: Tue, 15 Jul 2025 15:53:43 +0200
From: Peter Newman <peternewman@...gle.com>
To: Babu Moger <babu.moger@....com>
Cc: corbet@....net, tony.luck@...el.com, reinette.chatre@...el.com,
james.morse@....com, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
dave.hansen@...ux.intel.com, Dave.Martin@....com, x86@...nel.org,
hpa@...or.com, akpm@...ux-foundation.org, paulmck@...nel.org,
rostedt@...dmis.org, Neeraj.Upadhyay@....com, david@...hat.com, arnd@...db.de,
fvdl@...gle.com, seanjc@...gle.com, jpoimboe@...nel.org,
pawan.kumar.gupta@...ux.intel.com, xin@...or.com, manali.shukla@....com,
tao1.su@...ux.intel.com, sohil.mehta@...el.com, kai.huang@...el.com,
xiaoyao.li@...el.com, peterz@...radead.org, xin3.li@...el.com,
kan.liang@...ux.intel.com, mario.limonciello@....com, thomas.lendacky@....com,
perry.yuan@....com, gautham.shenoy@....com, chang.seok.bae@...el.com,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, eranian@...gle.com
Subject: Re: [PATCH v15 28/34] fs/resctrl: Introduce mbm_assign_on_mkdir to
enable assignments on mkdir
Hi Babu,
On Wed, Jul 9, 2025 at 12:22 AM Babu Moger <babu.moger@....com> wrote:
>
> The "mbm_event" counter assignment mode allows users to assign a hardware
> counter to an RMID, event pair and monitor the bandwidth as long as it is
> assigned.
>
> Introduce a user-configurable option that determines if a counter will
> automatically be assigned to an RMID, event pair when its associated
> monitor group is created via mkdir.
>
> Suggested-by: Peter Newman <peternewman@...gle.com>
> Signed-off-by: Babu Moger <babu.moger@....com>
> ---
> v15: Fixed the static checker warning in resctrl_mbm_assign_on_mkdir_write() reported in
> https://lore.kernel.org/lkml/dd4a1021-b996-438e-941c-69dfcea5f22a@intel.com/
>
> v14: Added rdtgroup_mutex in resctrl_mbm_assign_on_mkdir_show().
> Updated resctrl.rst for clarity.
> Fixed squashing of few previous changes.
> Added more code documentation.
>
> v13: Added Suggested-by tag.
> Resolved conflicts caused by the recent FS/ARCH code restructure.
> The rdtgroup.c/monitor.c file has now been split between the FS and ARCH directories.
>
> v12: New patch. Added after the discussion on the list.
> https://lore.kernel.org/lkml/CALPaoCh8siZKjL_3yvOYGL4cF_n_38KpUFgHVGbQ86nD+Q2_SA@mail.gmail.com/
> ---
> Documentation/filesystems/resctrl.rst | 16 ++++++++++
> fs/resctrl/monitor.c | 2 ++
> fs/resctrl/rdtgroup.c | 43 +++++++++++++++++++++++++++
> include/linux/resctrl.h | 3 ++
> 4 files changed, 64 insertions(+)
>
> diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
> index 06c8c08d0341..f9e9a8a66cae 100644
> --- a/Documentation/filesystems/resctrl.rst
> +++ b/Documentation/filesystems/resctrl.rst
> @@ -354,6 +354,22 @@ with the following files:
> # cat /sys/fs/resctrl/info/L3_MON/event_configs/mbm_total_bytes/event_filter
> local_reads,local_non_temporal_writes
>
> +"mbm_assign_on_mkdir":
> + Determines if a counter will automatically be assigned to an RMID, event pair
> + when its associated monitor group is created via mkdir. It is enabled by default
> + on boot and users can disable by writing to the interface.
> +
> + "0":
> + Auto assignment is disabled.
> + "1":
> + Auto assignment is enabled.
> +
> + Example::
> +
> + # echo 0 > /sys/fs/resctrl/info/L3_MON/mbm_assign_on_mkdir
> + # cat /sys/fs/resctrl/info/L3_MON/mbm_assign_on_mkdir
> + 0
> +
> "max_threshold_occupancy":
> Read/write file provides the largest value (in
> bytes) at which a previously used LLC_occupancy
> diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c
> index 0722e72f6cb1..ccca2330eebd 100644
> --- a/fs/resctrl/monitor.c
> +++ b/fs/resctrl/monitor.c
> @@ -984,6 +984,8 @@ int resctrl_mon_resource_init(void)
> resctrl_file_fflags_init("available_mbm_cntrs",
> RFTYPE_MON_INFO | RFTYPE_RES_CACHE);
> resctrl_file_fflags_init("event_filter", RFTYPE_ASSIGN_CONFIG);
> + resctrl_file_fflags_init("mbm_assign_on_mkdir", RFTYPE_MON_INFO |
> + RFTYPE_RES_CACHE);
> }
>
> return 0;
> diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
> index 4889e7556cc7..b7289ce2b3a6 100644
> --- a/fs/resctrl/rdtgroup.c
> +++ b/fs/resctrl/rdtgroup.c
> @@ -1987,6 +1987,42 @@ static ssize_t event_filter_write(struct kernfs_open_file *of, char *buf,
> return ret ?: nbytes;
> }
>
> +static int resctrl_mbm_assign_on_mkdir_show(struct kernfs_open_file *of,
> + struct seq_file *s, void *v)
> +{
> + struct rdt_resource *r = rdt_kn_parent_priv(of->kn);
> +
> + mutex_lock(&rdtgroup_mutex);
> + rdt_last_cmd_clear();
> +
> + seq_printf(s, "%u\n", r->mon.mbm_assign_on_mkdir);
> +
> + mutex_unlock(&rdtgroup_mutex);
> +
> + return 0;
> +}
> +
> +static ssize_t resctrl_mbm_assign_on_mkdir_write(struct kernfs_open_file *of,
> + char *buf, size_t nbytes, loff_t off)
> +{
> + struct rdt_resource *r = rdt_kn_parent_priv(of->kn);
> + bool value;
> + int ret;
> +
> + ret = kstrtobool(buf, &value);
> + if (ret)
> + return ret;
> +
> + mutex_lock(&rdtgroup_mutex);
> + rdt_last_cmd_clear();
> +
> + r->mon.mbm_assign_on_mkdir = value;
> +
> + mutex_unlock(&rdtgroup_mutex);
> +
> + return 0;
I noticed that "echo 0 > mbm_assign_on_mkdir" never completes. This
should return nbytes.
Thanks,
-Peter
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